A policy statement by the World Health Organization notes that, the male latex condom is the single, most efficient, available technology to reduce the transmission of HIV and other sexually transmitted infections. Unfortunately, despite decades of condom promotion efforts, condoms usage rates remain disappointingly low. Between one-third and one-half of men report poor condom fit, and these men are more likely to forego condom use. TheyFit LLC seeks to address this problem by manufacturing fitted condoms, with 95 different sizes available. Potential users can objectively determine their fitted condom size by using a paper measurement tool to determine their length and circumference measurements, thereby personalizing the condom sizing process. The proposed research will involve conducting a clinical trial to inform understanding of fitted condom safety performance (i.e. condom breakage and slippage), as well as addressing whether users perceive that fitted condoms enhance pleasure. This blinded trial will be conducted among diverse populations, allowing for assessment of condom performance for both anal and vaginal sex outcomes. This proposal will provide innovation by providing additional data to move condoms towards being regulated medical devices for anal sex. Additionally, this will be the first condom trial, to our knowledge, to explicitly assess pleasure as a primary endpoint. To maximize the public health benefits of increased condom options, we also propose to develop a mobile phone application (app) for automating the determination of fitted condom size. TheyFit will work in collaboration with faculty in Emory University's Departments of Epidemiology and Behavioral Sciences and Health Education, who have extensive expertise conducting clinical trial and related epidemiological research regarding HIV/AIDS among diverse populations. The proposed research has potential to inform efforts aimed at reducing HIV-related disparities and reducing new HIV infections, meeting two priority areas identified in the Strategic Plan of the NIH Office of AIDS Research.